Urgent tenant scenario, I need some help, possible squatter

[Steve Balinski]

I understand some of this is subject to state laws, but just want to get a general idea of where to go with this

2 tenants, both of them weren't getting along and decided one of them was going to move out, so I gave the other a 30 day notice to leave and signed the new lease with the one who was staying.  Today is day 28, the one who was supposed to leave is saying his plans fell through and he will need another month.  I had a bad feeling this person was going to end up being a squatter from the beginning, and now here we are.  I really don't want him to stay, but he basically told me he is staying and will need another month to come up with plan B and agreed by Nov. 1st he will be out.  Current lease states anyone living there not on the lease will incur a $xx/day fine.

My questions are: Can I amend a 1 year lease contract with the other person and make an amendment for the other person to stay for 1 month?

Can I charge an additional security deposit (month rent x2) because now I see him as very high risk?

How would I go about removing him without removing the good tenant who I re-signed with, is it the same eviction process?